1. Field of the Invention
The present invention relates to a method for controlling the locus of an arm of an arm-type robot or the like.
2. Description of the Prior Art
Since a multi-joint, arm-type robot has a high degree of freedom, is able to perform complex movements, and is capable of cooperative work with other such robots, it is employed for various purposes, including an industrial robot.
The movement of such an arm-type robot is usually controlled through the use of a PTP (Point-to-Point) system which controls the posture of the arm at successive but short intervals. In this case, however, if the intervals between individual control operations are long, the locus of the tip of the arm is disturbed by such nonlinear factors as centrifugal force, mutual interference and so forth during high-speed operations; therefore, this control system is not suitable for use in the case where an accurate locus is needed.
For a smooth and high-speed operation, the so-called open-loop control is better which solves an equation of motion of the arm taking into account the influences of the nonlinear factors and performs control.
With the open-loop control, however, accurate positioning is impossible due to the influence of variations in friction and so forth and, accordingly, it is necessary to employ means for solving such a problem.